As is well known, helicopter rotor blades must be rotated about their longitudinal axis to vary their lift. Achieving this function is difficult since the blades are mounted on a rotating shaft and thus are not only rotating about their own longitudinal axes, but a hub as well. Consequently, considerable complexity is required to convey power from a source fixed on the helicopter fuselage to rotate the blades in a controlled manner. It is even more difficult to get accurate position feedback of the rotative position of the blades back to the helicopter fuselage.
Heretofore, such control has been primarily accomplished through mechanical linkages extending through the actuators with position feedback signals being taken from the rotor head. The various configurations proposed are quite functional but have several drawbacks. The principal drawback is that of the need for a complicated linkage for driving the blades, in a controlled fashion, about their longitudinal axes. potential methods for performing this function include the use of electrical circuits having slip rings to transmit electrical power from a power source fixed in the helicopter fuselage to electrical actuators for the blades, pneumatic rotating joints to transmit fluid under pressure for actuating purposes, and in some limited instances, the use of hydraulic connectors to transmit hydraulic fluid under pressure. While possible, such methods are ineffectual and are more prone than is desired to partial or total failure.
A second drawback resides in such prior art systems of transmitting a position feedback signal from the actuator through a rotating joint to the control system for the rotor which typically is mounted on the fuselage. Slip rings provide very poor electrical feedback signals with the consequence that the ability to control the actuators positioning the blades cannot operate with the accuracy desired.
The present invention is directed to overcoming one or more of the above problems.